Low water alarm



Nov. 19, 1946.

F. M. PATTERSON LOW WATER ALARM Filed May 17,- 1944 )W70/MEMS.

Patented Nov. 19, 1946 Low WATER ALARM Frank M. Patterson, Pitman, N.` J. Application May 1v, 1944, serial No. 535,964

6 Claims.

The present invention relates to steam pressure equipment and more particularly to a low water alarm for steam boilers and the like.

Some of the objects of the present invention are: to provide an improved apparatus for responding to low water levels of a boiler as an indication thereof, or as a means for assuring prompt regulation of such level; to` provide a simple and sure means of protecting a boiler from low water conditions; to provide a device wherein an axially movable shaft is arranged to be shifted under a low water level to operate an alarm; to provide means including a rotating propeller within the boiler or water column for causing an alarm to sound When'the boiler level drops to a predetermined low; and t provide other improvements asv will hereinafter appear.

In the accompanying drawing, Fig. 1 represents a longitudinal section of a lowwater alarm embodying one form of the present invention; Fig. 2 represents a` sectional detail on line 2-2 of Fig. 1; Fig. 3 represents asection on line 3--3 of' Fig. 1; and Fig. 4 represents a side elevation of the device as installed on the water column of a boiler.

Referring to the drawing, one form of the present invention is shownl illustratively as used as a low water alarm for boilers, though the invention is not limited to the specific use since it is applicable to feed water regulators, high and low water alarms, steam traps, drainers and other pressure equipment. As shown, the device comprises a body I 0 arranged to be attached in leakproof relation to the side of a water column II of a boiler I2, at a point in alinement with the low water level. Bolts I3 secure the body I8 to the column II and a gasket I4 is interposed between the parts to make the joint pressure tight. The body IU has an extension I5 projecting through an opening I6 provided in the column I I, and through which a bore Il extends axially through the body I0. This bore I 1 forms a journal for a shaft I8 passing therethrough and projecting at both ends thereof. This shaft I8 is lubricated and maintained pressure tight by a gland of suitable packing material arranged to be forced into place by a supply duct 2| and feed screw 22. The end of the shaft I8, which enters the column Il, has a screw propeller 23 keyed thereon while the opposite end mounts a turbine 24 and a pair of bell clappers 25, the latter being carried by spring arms 26. The turbine 24 is mounted upon a square section 2'I of the shaft I8 to transmit motion to the shaft I8 but the arrangement is such that the shaft I8 can slide axially within limits provided by the annular box 28 encircling, the section 2'! and providing the necessary end clearances.

For housing the turbine 24, a closure cap` 30 iits about the turbine and has threaded connection with the. body I8. This cap 30 also forms a bearing 3l for the end of the shaft and is made pressure tight by a gland 32.. Steam is led to one side of the turbine 24 by a port 33 leading from' the interior of the column II', while an exhaust port 34 is provided at the opposite side of the turbine chamber.

For sounding an alarm when the boiler level reaches low water, a bell 35 is mounted upon the cap 30 to be in the path of the clappers 25 when the latter are in alarm, position, asV will beA explained. 1

For bringing the` bellclappers 25 into striking relation to` the bell 35, a plunger 36 having a cone shaped end is pressed against the end of the shaft I8 by a coil spring 3l bearing at. one end against a. collar on the plungerand atV the other endA against` a follower' 38 formed` as. a` part of a feed screw 4B' threaded through a supporting arm 4I and operated by a knurled. head 42.

In operation of theA device. the steamA pressureA maintains: theV turbine 24: rotating and as long as. the propeller 23 is operating in the water in the boiler it will shift and hold the shaft I8 (to the right as seen in Fig. 1) in a position overcoming the pressure of the spring 3l so that the clappers 25 are removed from the path of the bell 35. When the level of the water falls below the proper low point the propeller is then operating in a steam area and its thrust becomes ineffective to overcome the spring pressure, and the latter then shifts the shaft I8 (to the left as seen in Fig. 1) and the clappers I8 now strike the bell 35 and sound the alarm.

It will now be apparent that a complete unitary low water indicator has been devised wherein a positive and certain indication of a water level is obtained at all times and under all conditions. It should be noted that the propeller operates to maintain the device ineffective as long as the level is above the danger point but when the level falls below such point the propeller being in a steam area can no longer overcome the pressure of the thrust spring whereupon the latter actuates suitable alarm or other mechanism to result in the dangerous condition being corrected. While the turbine is here shown as driven by steam it can, as an alternative, be driven by a small electric motor or other means, as will be understood.

the differenceV in resistance between rotation in the two mediums taken as a measure of the liquid level. By using an electrical' circuit an ammeter could indicate the variation in load when passing from one medium to another.

Having thus described my invention, I claim:

l. In a low water alarm for boilers,.an indicator, an axially movable shaft entering the boiler I I propeller in a vessel subject to boiler pressure,

at a selected low water level, means for continuously rotating said shaft by fluid pressure within the boiler'regardless of level fluctuations, means operated by said shaft when the level falls below lsaid selected low water level for actuating said indicator, and means reacting to the water in the boiler to normally render said indicator operating means ineffective at levels above said low Water level.

2. In a low water alarm for boilers, an indicator, an axially movable shaft entering the boiler at a selected low water level, means for continuously rotating said shaft by uid pressure Within the boiler regardless of level fluctuations, means operated by said shaft when the level falls below said selected low water level for actuating said indicator, and means comprising a screw propeller on the shaft in the boiler to normally render said indicator operating means ineffective at levels Iabove said low water level.

3. In a low water alarm for boilers,` an indicator, an axially movable shaft entering the boiler at a selected `lovv level, means fo-r continuously rotating said shaft by fluid pressure within the boiler regardless of level fluctuations, a screw4 propeller on the shaft within the boiler reacting against the water to maintain said shaft in a position corresponding to a safe water level, a spring for moving said shaft to an alarm position when said level falls to bring said propeller into the steam space of the boiler, and means operated Joy said shaft in alarm position to operate said indicator.

4. In a low Water alarm for boilers, a screw propeller in a vessel subject to boiler pressure, a body attached exteriorly to said vessel, a shaft rotatably and slidably mounted on said body for mounting said propeller, said shaft being moved by the propeller-in one direction when immersedA in water, a spring for moving said shaft in the opposite direction when the propeller is in the steam space, means for continuously rotating said shaft by fluid pressure Within the boiler regardless of level fluctuations, and means `operated by the shaft for indicating a low Water condition.

5. In a low water alarm for boilers, a screw a body attached eXteriorly to said vessel, a shaft rotatably and slidably mounted on said body for mounting said propeller, said' shaft being axially f moved by the propeller in one direction when tinuously operating said turbine to rotate said shaft, a screw propeller on said shaft and Within the boiler to react against the Water in the boiler to maintain said shaftV in a position,corresponding to a safe water level, a spring -for movingk said shaft to an alarm position when said level falls below said selected low level tor bring said propeller into the steam space. of the boiler, and means operated by said shaft in alarm position to operate said indicator. n

FRANK M. PATTERSON. 

